Restoring and backing up infected pc after phishing scam?

Hello, Two days ago my parents got phished. My mom opened an email link from “the insurance”, which led to a bank page and she made a payment. 10 minutes later they get a call from “the bank” and the usual story happens: it was a scam link, but no need to panic, the friendly guy wants to help and remote connects to their pc… Afterwards my dad realises they’ve been fooled, and shuts down the pc, contacts the bank and police and closes their accounts and cards.

For now the damage is contained, most of the money transfers were blocked by the bank, and my parents updated their most important passwords (using their phones); but I don’t know exactly how to proceed cleaning the pc.

I’m bringing their pc home with me, keeping it disconnected from the internet (no wifi or ethernet) and copy all files to an external HDD, and then scanning the HDD for viruses.

How can I guarantee when I reconnect the HDD to my own pc, they don’t copy onto my HD? Is it enough to turn off autoplay to keep the virus from copying while I run a scan?

Can I download a virus scanner onto a flash drive and run that on the (probably) infected pc? Should I set up a guest network for my parents’ pc, and can I set it up using Ethernet? I know this is generally a good idea, but while my basic computer skills are good, setting up networks is new to me.

Which virus scanner would you guys recommend? I’m using Avira myself, combined with windows defender.

If all else fails, I would wipe the pc and reinstall windows, and copy the scanned and cleaned files from the HDD back on to it.